Application of ceramic membranes in water treatment for fish hatchery supplying purposes

Desalination 240 (2009) 117
126

Application of ceramic membranes in water treatment for fish hatchery supplying purposes Magdalena Szmukala, Daniela Szaniawska* Faculty of Food Science and Fisheries, Division of Environmental Science, Agricultural Academy of Szczecin, ul. K. Kazimierza 4B, 71-550 Szczecin, Poland Tel. +48 91 4231061; email: aksman@fish.ar.szczecin.pl, szaniawska@fish.ar.szczecin.pl Received 27 August 2007; revised 30 November 2007; accepted 7 December 2007

Abstract An experimental study was performed to assess the feasibility of treatment of surface water supplying small fish hatchery to water of desirable quality by cross-flow filtration and ceramic membranes. The experiments were performed using river water as a feed and two kinds of ceramic membranes as separation medium. Filtration tests were carried out at constant temperature (293 K) and various operating parameters such as cross-flow velocity and transmembrane pressure. The subject of analysis and discussion was the membrane selectivity from the point of view of simultaneous removal of selected contaminants as well as productivity of examined membranes. Finally, flux data obtained for filtration of deionized water and surface water were used for analysis in the frame of resistance-in-series model providing estimation of resistances characterizing examined systems, i.e. membrane hydraulic resistance, and reversible as well as irreversible fouling resistances. Keywords: Cross-flow membrane filtration; Ceramic membranes; Surface water treatment; Membrane fouling

1. Introduction The analysis carried out on surface water in Poland revealed a progressive increase of pollution content. In some rivers Polish standards on water quality for fish in natural condition are often exceeded. The fish hatcheries must solve *Corresponding author.

poor water quality problem by treatment natural water supplying the hatchery and breeding apparatuses. Thus, the proper water treatment schemes with respect to high demands on water quality, economical and environmental aspects are still the subject of research. An application of pressure driven membrane processes, namely ultra- or nanofiltration and inorganic membranes creates the various

Presented at the Third Membrane Science and Technology Conference of Visegrad Countries (PERMEA), Siofok, Hungary, 2–6 September 2007. 0011-9164/09/$– See front matter # 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2007.12.038

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possibilities in water treatment field. The attractiveness of using of membrane processes in natural water treatment is attributed to the improved performance and due to technological advances [1]. However, the major obstacle in the use of UF/NF units in water treatment is the problem of membrane fouling. To improve the filtration performance the cross-flow mode and highly permeable ceramic membranes can be used. Moreover, ceramic membranes have a high application potential because of their chemical, mechanical and thermal stability. Today, ceramic membranes with a cut-off between 1.0 and 3.0 kDa are available from several membrane producers, including TAMI, France. In this paper, the results of research on applicability of cross-flow filtration process using ceramic membranes with cut-off 1.0 and 3.0 kDa for treatment of natural surface water supplying the small fish hatchery are reported and discussed. The aim of the research is to test the feasibility of placing a cross-flow filtration unit with high permeable ceramic membranes in the multi-step treatment process for removing of selected impurities from river water. The selection of water quality parameters investigated in the research was done from the point of view of fish embryogenesis and breeding and Polish regulations on water quality. 2. Experimental 2.1. Surface water quality assessment The research on surface water quality supplying the fish hatchery in the Goleniow (Poland)

was performed in the year of 2005 (November
December) and 2006 (January
June). The water samples were taken for analysis once a month during the period of: 1. Autumn-spawning, November and December of 2005 and January and February of 2006 (sample numbers I
IV, Table 1) and 2. Spring-spawning, March
June of 2006 (sample numbers V
VIII, Table 1). Water supply system in the Goleniow fish hatchery is presented in Fig. 1. Surface water from Wisniowka River (1) supplies gravitationally the fish hatchery and breeding apparatuses (7) through weir (2), retention pond (3) and mechanical filters (4). The described water network operates in opened-loop mode. The used water is discharged, without treatment into the Wisniowka River. The selection of water quality parameters for analysis were conducted based on two Polish regulations, Decrees of Polish Ministry of Environment on water quality for fish in natural conditions [2] and on water quality for surface water classification [3]. It was necessary because Decree of Polish Ministry of Environment on water quality for fish in natural conditions do not determine limit values for ions, important from the point of view of fish embryogenesis and breeding, e.g. nitrate nitrogen, sulfates, calcium, magnesium, iron and bacteria. The limit values for chosen water quality indexes are presented in Table 2.

Table 1 Dates of sampling of surface water from Wisniowka River (Poland) Fish spawning

Autumn

Spring

Sample number

I

II

III

IV

V

VI

VII

VIII

Month Year

November 2005

December 2005

January 2006

February 2006

March 2006

April 2006

May 2006

June 2006

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M R M

F

P

Fig. 1. Water supply system in the Goleniow (Poland) fish hatchery: 1, Wisniowka river; 2, weir; 3, retention pond; 4, mechanical filters; 5, 6, place of sampling; and 7, fish hatchery and breeding apparatuses.

1

2

2.2. Nanofiltration tests The permeability and rejection measurements were carried out using laboratory scale membrane installation presented in Fig. 2. The feed was pumped from feed tank (1) through membrane Table 2 The limit values of water quality indicators for fish in natural conditions [2] and for surface water classification [3] Water quality index

Water Water requirement [2] requirement [3]

pH BOD (mg O2/dm3) CODMn (mg O2/dm3) Suspended solid (mg/dm3) Total P (mg P/dm3) Ammonia nitrogen 3 (mg /NHþ 4 /dm ) Nitrate nitrogen 3 (mg /NO 3 /dm ) Sulfates 3 (mg /SO2 4 /dm ) Calcium (mg Ca2+/dm3) Magnesium (mg Mg2+/dm3) Total iron (mg Fe/dm3) Number of coli bacteria (1/100 cm3)

6
9 B/3.0 / B/25 B/0.2 B/0.78

3

6.5
8.5 B/2.0 B/3.0 B/15 B/0.2 B/0.5

/

B/5

/

B/100

/

B/50

/

B/25

/

B/0.1

/

B/50

M F

Fig. 2. Schematic diagram of experimental installation: 1, feed tank; 2, pump; 3, membrane module; 4, heat exchanger; F, feed (surface water); P, permeate; R, retentate; and M, manometer.

module (3) and back through heat exchanger (4) to the feed tank. The membrane modules operated in cross-flow mode and permeate (P) and retentate (R) were recycled. Multilayered ceramic membranes (TAMI, CeRAM INSIDE) prepared of Al2O3/TiO2/ ZrO2 were used in the research. The characteristics and properties of the two kinds of membranes used in cross-flow filtration tests are presented in Table 3. The nanofiltration experiments were performed at constant temperature, 293 K. The pressure difference across the membrane, TMP, was adjusted at 0.55 and 0.85 MPa. Applied cross-flow velocity, u (feed velocity on membrane surface), were 4.0 and 5.7 m/s for 1.0 and 3.0 kDa membranes, respectively. The flow velocity was kept in highly turbulent regime with a Reynolds numbers of 14,000 and 34,000 for membrane with cut-off of 1.0 and 3.0 kDa, respectively. The rejection of selected water impurities in steady state conditions as well as permeate flux versus time were analyzed.

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Table 3 Characteristics of two kinds membranes used in the research

1.0 23 3.5

ðCF  CP Þ CF

TMP RM

1178 0.35 0.83/104

1178 0.2 1.53/104

ð1Þ

ð2Þ

Next, total resistance in the system, given by formula: RT ¼ RM þ RFre þ RFir

ð4Þ

ð5Þ

Finally, reversible fouling resistance, RFre was calculated as:

where CF and CP are contaminant content in feed and permeate, respectively. The two types of relationships between permeate flux and time were determined: (1) natural surface water with clean membrane (JV) and (2) deionized water flux with fouled membrane (JVk). In order to investigate the membrane fouling three transport resistances were calculated using resistance-in-series model [4,5]. First, the membrane resistance, RM, was determined using values of deionized water flux through clean membrane, JV0, and Darcy’s equation: JV0 ¼

RT

RFir ¼ ðTMP=JVk Þ  RM

3.0 8 6.0

The contaminant rejection, ri , was calculated using the formula: ri ¼

TMP

Data on deionized water flux through fouled membrane, JVk, allowed for evaluation of irreversible fouling resistance, RFir using formula:

Parameter

Cut-off (kDa) Number of channels Hydraulic diameter of channel (mm) Membrane length (mm) Membrane surface (m2) Membrane permeability (m3/m2 s MPa)

JV ¼

ð3Þ

was calculated using measured values of river water flux through clean membrane, JV, and resistance model equation:

RFre ¼ RT  RM  RFir

ð6Þ

The water samples for contaminant content analysis and surface water for cross-flow filtration experiments were picked up from water supply system in the Goleniow (Poland) fish hatchery after mechanical filters (point 5, Fig. 1) and after fish hatchery and breeding apparatuses (point 6, Fig. 1). 3. Results and discussion 3.1. Water quality indicators The water quality indicator values obtained for water samples taken from inlet (point 5, Fig. 1) and outlet (point 6, Fig. 1) of fish hatchery are shown in Tables 4 and 5, respectively. As it can be seen from these tables, the values of control parameters fluctuated considerably for both sets of samples. The analysis of mean values of water parameters presented in Tables 4 and 5 indicates that some water quality indicators exceed the limit values demanded for fish in natural conditions as well as for first class surface water. There are BOD, CODMn, suspended solid, total phosphorous, calcium, total iron and number of coli bacteria. The thesis was advanced that water quality indicators, such as BOD, suspended solid, total phosphorous, total iron and number of coli bacteria, should be rejected by investigated ceramic membrane to the extent satisfying demands of Polish regulations [2,3].

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Table 4 Fluctuation range of surface water parameters for samples I
VIII (Table 1) taken from inlet of fish hatchery and breeding apparatuses (point 5, Fig. 1) Parameter

Max. value

Min. value

Mean value

Temperature pH BOD (mg O2/dm3) CODMn (mg O2/dm3) Suspended solid (mg/dm3) Total P (mg P/dm3) 3 Ammonia nitrogen (mg /NHþ 4 /dm )  3 Nitrate nitrogen (mg /NO3 /dm ) 3 Sulfates (mg /SO2 4 /dm ) 2+ 3 Calcium (mg Ca /dm ) Magnesium (mg Mg2+/dm3) Total iron (mg Fe/dm3) Number of coli bacteria (1/100 cm3)

16.3 8.34 9.7 13.3 1000 0.430 0.164 0.218 123 129.9 34.9 0.430 12,000

0.5 7.31 2.4 7.4 90 0.170 0.065 0.058 20.4 83.6 10.0 0.065 550

6.28 8.05 5.03 9.9 371 0.280 0.100 0.138 59.8 101.5 20.06 0.220 3200

The comparison of the results presented in Tables 4 and 5 indicates that fish embryogenesis and breeding had little influence on control water quality indicators. It can be seen from these tables that noticeable increase of indicator value was observed for three water parameters, i.e. number of coli bacteria (47%), ammonia nitrogen (23%)

and total iron (19%). The most toxic for fish embryogenesis and breeding is ammonia ion due to the possibility of forming of no ionized NH3. For example, for pH 8.0 and temperature 208C about 5% of NHþ 4 will be in the form of NH3. Acceptable for fish concentration of no ionized ammonia is very low, 0.021 mg/dm3. This limit /

/

Table 5 Fluctuation range of surface water parameters for samples I
VIII (Table 1) taken from outlet of fish hatchery and breeding apparatuses (point 6, Fig. 1) Parameter Temperature pH BOD (mg O2/dm3) CODMn (mg O2/dm3) Suspended solid (mg/dm3) Total P (mg P/dm3) 3 Ammonia nitrogen (mg /NHþ 4 /dm )  3 Nitrate nitrogen (mg /NO3 /dm ) 3 Sulfates (mg /SO2 4 /dm ) 2+ 3 Calcium (mg Ca /dm ) Magnesium (mg Mg2+/dm3) Total iron (mg Fe/dm3) Number of coli bacteria (1/100 cm3)

Max. value 16.8 8.28 6.2 13.1 950 0.440 0.223 0.240 128 131.6 37.7 0.740 22,000

Min. value 0.1 7.68 2.2 7.2 80 0.240 0.074 0.060 23 87.4 12.4 0.105 1800

Mean value 6.42 7.98 4.4 9.5 367 0.320 0.131 0.146 71.3 103.7 22.7 0.270 6000

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was not exceeded in samples from River Wisniowka. The concentration of total iron in water bigger then 0.5 mg/dm3 can create adverse conditions for fish embryogenesis due to lack of oxygen. Similarly, excess of suspended solid is undesirable for fish embryogenesis [6]. 3.2. Contaminant rejection The rejection results obtained using as feed water taken from inlet and outlet of fish hatchery for both investigated membranes, 1.0 and 3.0 kDa, are summarized in Tables 6 and 7, respectively. As it can be seen from Tables 6 and 7, the advanced thesis has been proved correct in the case of some water parameters important from the point of view of fish embryogenesis, i.e.: BOD, total P and total iron, which are rejected to required limits

by both 1.0 and 3.0 kDa membranes. The rejection results were obtained at transmembrane pressure (TMP) of 0.55 and 0.85 MPa and cross-flow velocity 4.0 and 5.7 m/s for 1.0 and 3.0 kDa membranes, respectively. For full characterization of membrane performance data on dependence of permeate flux on pressure difference across the membrane, crossflow velocity and time are needed. Data on membrane selectivity and permeability versus operating parameters are crucial for practical application where finding of optimal compromise between two requirements, high rejection and high permeability, is necessary. 3.3. Permeate flux and fouling The long term (about 2 h) cross-flow filtration test using water taken from inlet of fish hatchery

Table 6 Contaminant content in feed, CF, and permeate, CP, and contaminant rejection, ri , by ceramic membrane with cut-off 1.0 and 3.0 kDa for samples III and VI (Table 1); water taken from inlet of fish hatchery and breeding apparatuses (point 5, Fig. 1) TMP (MPa) Parameter

0.55 Water requirement [2]

0.85

CF

CP

ri (%)

CF

8.03 6.5 12.2 140 0.31 0.28 10,800

8.00 0.5 6.7 0 0.13 0 108


92 45 100 58 100 99

7.00 8.05 5.8 0.6 10.0 6.7 290 40.6 0.35 0.18 0.31 0.04 9800 294


89 33 86 48 86 97

8.06 4.3 11.5 190 0.35 0.41 11,500

8.12 1.4 7.5 17.1 0.21 0.09 115


68 35 91 39 79 99

8.28 8.11 3.6 1.8 8.8 6.7 320 93 0.24 0.15 0.25 0.07 6500 130


49 24 71 36 73 98

CP

ri (%)

[3]

1.0-kDa membrane, cross-flow velocity u/4.0 m/s pH 6
9 B/3.0 BOD (mg O2/dm3)
CODMn (mg O2/dm3) B/25 Suspended solid (mg/dm3) B/0.2 Total P (mg P/dm3)
Total iron (mg Fe/dm3) Number of coli bacteria (1/100 cm3)


6.5
8.5 B/2.0 B/3.0 B/15 B/0.2 B/0.1 B/50

3.0-kDa membrane, cross-flow velocity u/5.7 m/s pH 6
9 B/3.0 BOD (mg O2/dm3)
CODMn (mg O2/dm3) B/25 Suspended solid (mg/dm3) B/0.2 Total P (mg P/dm3)
Total iron (mg Fe/dm3) Number of coli bacteria (1/100 cm3)


6.5
8.5 B/2.0 B/3.0 B/15 B/0.2 B/0.1 B/50

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Table 7 Contaminant content in feed, CF, and permeate, CP, and contaminant rejection, ri , by ceramic membrane with cut-off 1.0 and 3.0 kDa for samples III and VI (Table 1); water taken from outlet of fish hatchery and breeding apparatuses (point 6, Fig. 1) TMP (MPa) Parameter

0.55 Water requirement [2]

CF

0.85 CP

ri (%)

CF

CP

ri (%)

[3]

1.0-kDa membrane, cross-flow velocity u/4.0 m/s pH BOD (mg O2/dm3) CODMn (mg O2/dm3) Suspended solid (mg/dm3) Total P (mg P/dm3) Total iron (mg Fe/dm3) Number of coli bacteria (1/100 cm3)

6
9 B/3.0 / B/25 B/0.2 / /

6.5
8.5 B/2.0 B/3.0 B/15 B/0.2 B/0.1 B/50

7.98 7.84 5.2 0.3 11.2 5.8 810 43 0.39 0.18 0.53 0 13,500 97

/ 94 48 95 53 100 99

8.05 7.93 6.0 0.84 9.7 6.3 750 97.5 0.35 0.20 0.45 0.05 8400 336

/ 86 35 87 43 89 96

6.5
8.5 B/2.0 B/3.0 B/15 B/0.2 B/0.1 B/50

8.12 8.13 4.8 1.4 10.9 8.17 570 108 0.40 0.23 0.63 0.09 17,000 850

/ 71 25 81 43 86 95

7.84 7.80 3.7 1.6 9.4 7.6 480 144 0.27 0.19 0.58 0.14 5800 348

/ 57 20 70 30 76 94

3.0-kDa membrane, cross-flow velocity u/5.7 m/s pH BOD (mg O2/dm3) CODMn (mg O2/dm3) Suspended solid (mg/dm3) Total P (mg P/dm3) Total iron (mg Fe/dm3) Number of coli bacteria (1/100 cm3)

6
9 B/3.0 / B/25 B/0.2 / /

and breeding apparatuses were performed. During the cross-flow filtration studies, the decline in permeate flux typical for pressure-driven membrane processes was observed. The permeate flux declined with time to pseudo-steady state values for both investigated membranes. The producer (TAMI) values of JV0 and experimental values of JV and JVk for investigated membranes and levels of operating parameters are summarized in Table 8. The relationships of permeate flux versus time for water (JV0, JVk) and surface water (JV) cross-flow filtration through clean and fouled membranes are presented graphically in Fig. 3(a) and (b) for 1.0 and 3.0 kDa membranes, respectively.

Using values of JV0, JV and JVk presented in Table 8, the mean values of characteristic fluxes were calculated. Next, characteristic resistances, RM, RFre, RFir, for investigated membranes and levels of operating parameters were evaluated using Eqs. (2)
(6). The obtained results are shown in Tables 9 and 10 as well as in Fig. 4(a) and (b) for 1.0 and 3.0 kDa membranes, respectively. It can be seen from Fig. 4 that fouling resistances, RFre and RFir, achieved lower values for higher TMP for both investigated membranes. Moreover, it is visible that better conditions for high flux (low total resistance) exist in the system with 3.0 kDa membrane. It can be attributed to the fact that employing of 3.0-kDa

M. Szmukala, D. Szaniawska / Desalination 240 (2009) 117
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(a) 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00

JV (m3/m2s) × 10–4

JV (m3/m2s) × 10–4

124

1.20 1.00 0.80 0.60 0.40 0.20 0.00

0

50

100

150

200 250 Time (min)

300

350

JV0 TMP = 0.55 MPa JV TMP = 0.55 MPa

JV0 TMP = 0.85 MPa JV TMP = 0.85 MPa

JVk TMP = 0.55 MPa

JVk TMP = 0.85 MPa

400

450

0

50

100

150

200 250 Time (min)

300

350

400

450

Fig. 3. Permeate flux versus time for cross-flow filtration of deionized water (JV0, JVk) and river water (JV) with clean and fouled membranes: (a) 1.0 kDa; TMP/0.55, 0.85 MPa; u/4.0 m/s and (b) 3.0 kDa; TMP/0.55 and 0.85 MPa; u/5.7 m/s.

membrane enables to use higher cross-flow velocity, u 5.7 m/s. /

4. Conclusions The selected water quality parameters characterizing surface water supplying fish hatchery

in Goleniow (Poland) were monitored over 1 year obeying autumn- and spring-spawning. The values of water quality parameters important for fish embryogenesis and breeding were analyzed and compared with requirements of Polish Ministry of Environment on water quality. It was found that some water indicators, i.e. BOD,

Table 8 The producer value of JV0 and experimental values of JV and JVk for investigated membranes and levels of operating parameters Membrane cut-off

u (m/s)

TMP (MPa)

JV0 /104 (m3/m2 s)

JV /104 (m3/m2 s)

JVk /104 (m3/m2 s)

1 kDa

4.0

0.55

0.46 0.46 0.46 0.46 0.70 0.70 0.70 0.70 0.84 0.84 0.84 0.84 1.30 1.30 1.30 1.30

0.22 0.16 0.24 0.19 0.36 0.55 0.43 0.48 0.48 0.32 0.42 0.44 0.72 1.08 1.02 0.69

0.33 0.24 0.29 0.24 0.51 0.59 0.54 0.57 0.62 0.48 0.58 0.60 0.82 1.26 1.22 0.78

0.85

3 kDa

5.7

0.55

0.85

125

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126 Table 9 Mean values of fluxes, JV0, JV, JVk, and calculated values of resistances, RM, RFre, RFir, for membrane with cut-off 1.0 kDa

Table 10 Mean values of fluxes, JV0, JV, JVk, and calculated values of resistances, RM, RFre, RFir, for membrane with cut-off 3.0 kDa

TMP (MPa)

0.55

0.85

TMP (MPa)

0.55

0.85

u (m/s) JV0 /104 (m3/m2 s) JV /104 (m3/m2 s) JVk /104 (m3/m2 s) RM (MPa m2 s/m3) RFre (MPa m2 s/m3) RFir (MPa m2 s/m3)

4.0 0.46 0.20 0.28 1.2/104 0.79/104 0.77/104

4.0 0.70 0.46 0.55 1.2/104 0.30/104 0.33/104

u (m/s) JV0 /104 (m3/m2 s) JV /104 (m3/m2 s) JVk /104 (m3/m2 s) RM (MPa m2 s/m3) RFre (MPa m2 s/m3) RFir (MPa m2 s/m3)

5.7 0.84 0.42 0.57 0.65/104 0.31/104 0.31/104

5.7 1.3 0.89 1.02 0.65/104 0.12/104 0.18/104

The limit values for fish water regulation could not be reached in one treatment step. It would be now necessary to investigate combination of membrane filtration process with another one for sufficient elimination of CODMn. The resistance-in-series model was used for evaluation fouling phenomenon in investigated membrane systems with the aim of comparison of permeability of both membranes. The results of fouling analysis indicate that the increase of TMP from 0.55 to 0.85 MPa results in decrease

(a) 14000

(b) 7000

12000

6000

10000

5000

R i (MPa m 2 s/m 3 )

R i (MPa m 2s/m 3)

CODMn, suspended solids, total P and total iron, exceeded water limits. Rejection of basic contaminants by ceramic 1.0 and 3.0 kDa membranes in cross-flow filtration of surface water were investigated. Some contaminants such as BOD, total phosphorous and total iron were rejected to required limits by both 1.0 and 3.0 kDa membranes under investigated TMP and cross-flow velocity. Unfortunately, the used membranes have showed their limits for CODMn elimination to desirable level.

8000 6000 4000 2000

4000 3000 2000 1000

0

0.55 0.85 TMP (MPa) RM

RFre

0 0.55 0.85 TMP (MPa)

RFir

Fig. 4. Comparison of characteristic resistances, RM, RFre, RFir: (a) membrane with cut-off 1.0 kDa, u/4.0 m/s; (b) membrane with cut-off 3.0 kDa, u/5.7 m/s.

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in fouling resistances for both 1.0 and 3.0 kDa membranes. Moreover, fouling resistance for the 3.0-kDa membrane is lower in comparison with the 1.0-kDa one. Since rejection results were similar for both membranes, looser membrane could be employed for removal of contaminants undesirable for fish embryogenesis and breeding to the limits demanded by Polish water quality regulations. Additional gain would be higher flux and smaller membrane area needed for practical implementation. Nomenclature BOD CODMn CF CP F JV JV0 JVk M P ri

biological oxygen demand (mg O2/ dm3) chemical oxygen demand (mg O2/dm3) contaminant concentration in feed, Eq. (1) contaminant concentration in permeate, Eq. (1) feed surface water flux, Eq. (4) (m3/m2s) deionized water flux through clean membrane, Eq. (2) (m3/m2s) deionized water flux through fouled membrane, Eq. (5) (m3/m2s) manometer permeate contaminant i rejection, Eq. (1)

R RFir RFre RT RM TMP u

retentate irreversible fouling resistance, Eq. (5) (MPa m2 s/m3) reversible fouling resistance, Eq. (6) (MPa m2 s/m3) total resistance, Eq. (3) (MPa m2 s/m3) membrane resistance, Eq. (2) (MPa m2 s/m3) transmembrane pressure, Eq. (2) (MPa) cross-flow velocity (m/s)

References [1]

[2]

[3]

[4] [5] [6]

K. Scott, Handbook of Industrial Membranes, second ed., Elsevier Advanced Technology, New York, 1998. Regulation of Polish Ministry of Environment dated 4 October 2002 in the case of water quality for fish in natural conditions. J. Law, No.176, item1455 (Dz. U. Nr 176, poz.1455). Regulation of Polish Ministry of Environment dated 11 February 2004 and 4 October 2002 in the case of water quality for surface water classification, J. Law, No. 32, item 284 (Dz. U. Nr 32, poz.284). K.M. Ko and J.J. Pellegrino, J. Membr. Sci., 74 (1992) 141
157. A.P. Perkin, M.K. Ko and J.J. Pellegrino, J. Membr. Sci., 60 (1991) 195
206.  J. Szczerbowski, Inland fisheries in Poland, IRS, Olsztyn, 1993 (in Polish).